Immunoglobulin structure and diversity: 1) Amino acid sequence analysis of a series of hybridomas with specificity for beta(1,6) galactan is in progress to evaluate structure, function and idiotype. Nucleic acid probes are being developed to characterize the gene structures coding for these proteins. 2) Amino acid sequence analysis of antigen binding variants of a phosphorylcholine binding myeloma has demonstrated that single amino acid substitutions in framework regions as well as complementarity determining regions may alter antigen binding specificity providing a potential model for somatic mutation in the generation of antibody diversity. II. Cell membrane proteins: Papain fragments have been prepared and purified from the major transplantation antigens obtained from two of our inbred herds of miniature swine. Amino terminal sequences have been obtained for the heavy chains as well as the associated beta2-microglobulin. DNA probes have been used to characterize the genes coding for these antigens by Southern blot analysis and to isolate genomic clones containing transplantation antigen sequences.